This invention relates to the preparation of formamides and more particularly to the preparation of aromatic formamides by the reaction of aromatic amines with carbon monoxide.
Formamides are valuable as industrial solvents and as starting materials for the preparation of important chemical intermediates and finished chemicals, such as isocyanates. Increasing interest in formamides has led to investigations for more economical and efficient processes for their production. Much recent research has been directed to the preparation of formamides by the carbonylation reaction between amines and carbon monoxide using various metal catalysts. Unfortunately, these reactions have been generally catalyzed by expensive Group VIII noble metal catalysts, such as the salts of palladium and platinum. Some success has been observed in the carbonylation of aliphatic and heterocyclic amines to formamides with carbon monoxide using relatively inexpensive copper salts, however, these catalysts were found not to be effective in catalyzing the reaction of aromatic amines with carbon monoxide to produce aromatic formamides (U.S. Pat. No. 2,677,706; T. Saegusa et al, Tetrahedron Letters, Vol. 49, pp 6125-6129 (1966); T. Saegusa et al, Bull. Chem. Soc. Japan, Vol. 42, pp 2610-2614 (1969); B. Nefedov et al, Izv. Akad. Nauk. S.S.S.R. Ser Khim, No. 7, pp 1536-1540, July 1973). Since carbon monoxide is a very inexpensive starting material and copper salts are relatively inexpensive catalysts, the preparation of formamides from amines and carbon monoxide using copper salt catalysts is potentially of considerable economic importance. Accordingly, it would be desirable to adapt this procedure to the preparation of aromatic formamides from aromatic amines.